How much chlorine do I need to kill algae, given these parameters?

Pump should be running for 30 minutes prior to taking samples for testing.

If you do not clean out any algae hiding in light niches, ladders, weir doors, etc, you will have random overnight FC loss. Eradicating the algae then maintaining FC based on CYA keeps the pool clean of algae. My pool has never had algae.
 
In my experience it doesn't matter much when I run the pump. Especially if I keep the solar cover on it. It just matters to make sure that the chlorine is getting mixed in really well before it shuts off, otherwise you're going to have areas of your pool that are basically untreated water and that's where you'll tend to find some algae blooms. I have a corner that has really poor circulation that tends to get mustard algae every now and then. Or, rather, I DID, I'm hoping after this remodel that will be taken care of with the new directional fittings.

If I could afford to run my pump 24/7 I would. When SMUD's time of day rates changes on Oct. 1st I will be running it about 3 hours in morning and 3 hours in evening, and then I will change to dosing the pool in the PM to give the chlorine a little longer to do it's magic in the dark.
 
So, what you're saying is that there's no science behind WHEN to run the pump to prevent chlorine loss.

As I mentioned, I wait 2 hours after adding chemicals before testing, but what about what I said about morning tests, when chemicals are not added? That seems to be where the tests fluctuate a LOT!
Not that I can ascertain either.. The SMUD "Time of Day" BS dictates when I run my pump. I haven't really found any correlation as to when to run it. Other than make sure it's running when you add LC. LC being more dense than water will pool on the bottom unless mixed. But I don't think there is enough time within the schedule of a pool pump to create a "cline" of chlorine. I created a chlorine-cline once when my pump motor died and I religiously added LC since my SWG wasn't running. Apparently my sweeping/brushing wasn't providing enough mixing.. when I finally got a new pump on line my LC levels hit the moon.. it had been sitting on the bottom the whole time... plankton (zoo and phyto) will migrate up and down in the water column on a diurnal cycle (it was the subject of my thesis).. but in a pool there is not a whole lotta places for it to go... and plus its being artificially mixed pretty regularly.
that's my dos centavos based on my back yard experiment.
 
Hmmm, since circulation may not be perfect, and chlorine sinks, I should probably be taking water samples from the same spot in the pool every time. After all, tests are based on constants, duh! I should have thought about that before. Oh well, at least I thought about it now!
 
Pump should be running for 30 minutes prior to taking samples for testing.
I just re-read this. Does this apply to even when you didn't add anything? For example, I dose at night, and understandably the pump should run for a while before testing. But, when I check in the morning, even without having added anything, are you saying I should run the pump for 30 minutes prior to testing?

If this is indeed what you mean, then it makes sense why I recorded a 1.5ppm loss overnight that one time; the pump had been running continuously from when I dosed the prior evening until after I tested again the next morning. The other huge overnight losses that were all over the board were recorded in the morning after the pump had been off for many hours. If chlorine tends to settle lower in the water column, then it makes much more sense to run the pump for awhile before testing than just draw samples from the same spot.
 
I just re-read this. Does this apply to even when you didn't add anything? For example, I dose at night, an understandably pump should run for a while before testing. But, when I check in the morning, even without having added anything, I should run the pump for 30 minutes prior to testing?

If this is indeed what you mean, then it makes sense why I recorded a 1.5ppm loss overnight that one time; the pump had been running continuously from when I dosed the prior evening until after I tested again the next morning. The other huge overnight losses that were all over the board were recorded in the morning after the pump had been off for many hours. If chlorine tends to settle lower in the water column, then it makes much more sense to run the pump for awhile before testing than just draw samples from the same spot.

Yes, still water gets stratified. Mix it up before checking chemicals.
 
There should be a single screw that when removed the light pops out of the niche.

If the light ash not been removed in a long time that screw can become difficult to remove. If you break the screw or strip it note that it is a special screw. There is a product called Light Wedge if the screw hole becomes stripped.
I've always been afraid to touch the lights for fear of killing myself, so have no idea what it looks like behind them. Do I just ensure the light switch is off, and then go for it, underwater? I do have one bulb out, too, so maybe this is a good time to change it. Any instructions on this process would be appreciated.
 
I've always been afraid to touch the lights for fear of killing myself, so have no idea what it looks like behind them. Do I just ensure the light switch is off, and then go for it, underwater? I do have one bulb out, too, so maybe this is a good time to change it. Any instructions on this process would be appreciated.

Turn off the light CB. Confirm you have a GFCI CB on the light.

Changing the light bulb depends on exactly what model light housing you have. There are likely YouTube videos on how to change the bulb. The challenge is ensuring you have a waterproof seal on the light housing after reassembling it.
 
I don't know what CB is, but after looking at some YouTube videos, it looks like standard lights simply consist of a floodlight in a housing on a long wire. I thought they'd be more complicated than that. I guess I have to take out the housing to see what I need. Looks like there are some color changing led bulbs I might be able to replace with, too. I just hope over all these years, there's still a model number or some spec marking on the bulb and gasket.
 

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CB = Circuit Breaker

Usually there is enough wire coiled behind the housing to pull it out of the water and onto the deck to work on it.
 
Wouldn't simply turning off the light switch be good enough?

No, turn off the circuit breaker for safety. I am not going to go through the ways the switch can be miswired and a wire hot with the light off.
 
OK, thanks. I thought the switch would've cut power to the light completely, but if there is even the possibility of power still being in the circuit, I would not want to test that!

When working around electricity never assume.
 
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